In a major plot twist, the “Game On” episode of Showtime’s “Homeland” reveals that case officer Carrie Mathison (Claire Danes) is working undercover to expose the key terrorist behind the CIA headquarters bombing.

For the elaborate ruse to succeed, CIA Acting Director Saul Berenson (Mandy Patinkin) scapegoats Carrie before a hostile Senate committee, confines her to a psychiatric ward, freezes her bank account, invalidates her passport, adds her to the No-Fly List and puts her home under surveillance.

These draconian measures convince ethically challenged attorney Leland Bennett (Martin Donovan) that Carrie is vulnerable, bitter and lacking options. In other words, she’s primed to become a confidential informant.

What Carrie must do in exchange for the law firm’s protection is share a few spy agency secrets with Leland’s client, a high-ranking Iranian intelligence official. Specifically, the client wants to know how the CIA identified and assassinated six of his colleagues.

The CIA will destroy Carrie, Leland predicts, by leaking her name to the news media. And if she doesn’t commit suicide, she’ll eventually die in a CIA-arranged “accident.”

“Let us help you, Carrie,” Leland offers. “We’re very good at it.”

Carrie agrees to Leland’s proposal under one condition: She must meet his mysterious client face to face.

“It worked, Saul,” Carrie says after covertly making her way to Saul's home.

“You’ve been very, very brave,” he says as she sobs in his arms.

“It’s too hard,” she protests. “I can’t keep going.”

“Yes you can,” Saul replies, assuring her that the undercover assignment is almost over.

So it’s game on indeed as Saul and Carrie close in on the Iranian terrorist. Helping them investigate the suspect is CIA analyst Fara (Nazanin Boniadi), who determined that the official stole $45 million from Iran’s Revolutionary Guard over the last decade by skimming illegal money transfers.

Fara advocates swift justice, but Saul is concerned with the bigger picture. He wants the official to disclose the names of spies operating in the U.S. and reveal how close the Iranian government is to developing nuclear weapons.

“I need him in a room,” Saul tells Fara. “I want to rip him down to the studs.”

Another major plot twist involves Brody’s troubled daughter Dana (Morgan Saylor) as she abets boyfriend Leo Carras (Sam Underwood) in escaping from a rehabilitation clinic. Dana steals a car from her mom, Jessica (Morena Baccarin), swaps vehicles at a sleazy garage and is off to begin a new life with Leo.

Among the stops on their furtive road trip is the cemetery where Leo’s younger brother is buried. He supposedly committed suicide, but Leo feels responsible.

But maybe Leo is to blame -- and maybe it wasn’t suicide -- according to records obtained by Jessica’s lover, Marine Corps Maj. Mike Faber (Diego Klattenhoff). Authorities, it seems, confined Leo to the clinic in lieu of prosecuting him for his brother’s death.

Poor Dana! Not only is her dad the world’s most wanted fugitive, her new beau just might be a murderer!